Conventional optical spectroscopy of flowing fluids is generally performed via an optical probe device that is inserted through a port into a fluid flow region. These optical probe devices can include a ‘window’ optical element, e.g., a non-refractive optical element that typically can be disposed between the refractive optical elements of the optical probe device and the sample flow, e.g., the optical probe device can have a tip that is inserted through a port into the flow, wherein the tip can include a window element to protect the refractive optical elements within the optical probe device.